The instant invention relates to thermally activated valves and more particularly to a valve which is operative with a snap-action action in response to a predetermined temperature condition for controlling a fluid flow.
A variety of different types of thermally activated valves have been heretofore available for use in various specific applications. For example, thermally activated valves have been heretofore available for use in automatic automotive transmissions in order to prevent the flow of transmission fluids under certain operating conditions. Specifically, they have been utilized for preventing the flow of transmission fluids through the torque converter sections of automatic transmission before suitable fluid operating temperature levels are reached. In this connection, however, it has been found that for applications of this general type, in order to avoid equipment damage, thermally activated valves must be highly reliable, and they must be highly sensitive to fluid temperature changes, although they must be relatively insensitive to fluid pressure changes.
Thermally activated devices representing the closest prior art to the subject invention of which the applicant is aware are disclosed in the U.S. Pat. Nos. to Ludwig, Re.30,552; Zinkle, 2,271,850; Frumet, Jr., 2,742,927; O'Hara et al, 3,411,712; Meulendyk et al, 3,587,967; Soberski, 3,612,018; Myers, 3,687,290; McIntire, 3,804,326; Schneider, 3,853,268; Doherty, Jr., 3,856,259; Place, 3,930,613 and Bible, 3,963,042. However, since these references fail to teach a thermally activated snap-action valve which is operative with a high level of sensitivity and reliability in the manner of the snap-action valve of the instant invention, they are believed to be of only general interest with respect thereto.
The instant invention provides a reliable thermally activated snap-action valve which is highly sensitive to fluid temperature changes but relatively insensitive to fluid pressure changes, and which therefore can be effectively utilized for applications such as in automatic transmissions. Specifically, the thermally activated snap-action valve of the instant invention comprises a valve body having an interior cavity formed therein and inlet and outlet passages which communicate with the cavity, a valve seat adjacent the inner end of the outlet passage, and a ball element in the cavity which is receivable in a closed position in the valve seat for obstructing the flow of fluid therethrough. The valve further comprises a resilient positioning plate which is operative for positioning the ball element so that it is normally disposed in an open position wherein it is spaced inwardly from the valve seat, but so that it is resiliently movable to a closed position wherein it obstructs the valve seat. The thermally activated valve of the instant invention further comprises a bimetallic disc in the cavity which is operative with a snap action in response to a predetermined temperature condition and communicates with the ball element for moving the ball element from the open position thereof to the closed position thereof in response to the predetermined temperature condition. The bimetallic disc is preferably mounted on a shoulder which is formed in the valve body in the cavity, and the valve body is preferably formed so that it has a plurality of fluid passages therein which are spaced around the perimeter of the bimetallic disc for allowing a fluid to pass through the cavity from the inlet passage to the outlet passage. As a result, the fluid pressures on the opposite sides of the bimetallic disc are always maintained at substantially equal levels so that the effects of fluid pressures on the bimetallic disc are minimal. The resilient spring plate (also not effected by fluid pressure) which is operative for positioning the ball element in the cavity is preferably integrally blanked from a resilient sheet metal, and it comprises a central portion having a central aperture therein, and a plurality of resilient arms which extend outwardly from the central portion. The ball element is received and supported in the central aperture in the spring plate, and the resilient arms are preferably supported by a second shoulder which is formed in the valve body adjacent the valve seat. Further, a reduced cavity section is preferably formed in the valve body adjacent the inner end of the outlet passage, and the valve seat is preferably defined by a valve seat member which is received in the reduced cavity section so that fluid passing through the cavity must pass through the valve seat member prior to passing outwardly through the outlet passage. The snap-action valve preferably further comprises a resilient spring washer which is received in the reduced cavity section adjacent the inner end of the outlet passage for cushioning the valve seat member so that the valve seat member is slightly resiliently deflectable in response to a force applied thereto by the bimetallic disc through the ball element when the ball element is in the closed position.
During use and operation of the snap-action valve of the instant invention, a fluid passing through the cavity in the valve body is maintained in intimate contact with the bimetallic disc so that the temperature of the bimetallic disc is always maintained at essentially the same level as the temperature of the fluid, and as a result, the snap-action valve of the instant invention is extremely sensitive to temperature changes. Further, since the valve is constructed so that the fluid pressures on the opposite sides of the bimetallic disc (and the resilient spring plate) are always maintained at essentially equal levels, the valve is relatively insensitive to fluid pressure changes. Still further, since the snap-action valve of the instant invention is operative with a positive switching action utilizing a minimum of moving parts, it is highly reliable, and it can be effectively utilized in a variety of applications.
Accordingly, it is a primary object of the instant invention to provide an effective and reliable thermally activated snap-action valve.
Another object of the instant invention is to provide an effective snap-action valve which is highly sensitive to fluid temperature changes.
An even further object of the instant invention is to provide an effective snap-action valve which is essentially uneffected by fluid pressure changes.
Other objects, features and advantages of the invention shall become apparent as the description thereof proceeds when considered in connection with the accompanying illustrative drawings.